Gems are collected through levels and are the primary currency for unlocking new Prisoners, but can be traded for anything. Each level containts 3 to 7 Gems (+2 if you get A++ rating).

Freeing new Prisoners will cost 10 Gems each, but the price will rise depending on your Current Prisoner Count and your Current Prisoner Count of that Head Shape up to 30 Gems.

There are 252 Prisoners to be unlocked with Gems (63 Prisoners per shape).

If you complete the main story mode in both solo and coop on Normal and Insane mode with A++ rating you will still need to play Furbottom Feature weekly or Arena mode to earn enough gems for all the prisoners as you can only get about 4000 Gems from the story levels.

In total you need 4640 - 4795 Gems, depending on how you purchase the prisoners. It is recommended to always purchase the ones that cost less than others first.

Some Gems can be found hidden inside of fake blocks.

https://steamhost.cn/steamcommunity_com/id/Freekill/inventory/#238460_2_51286660

Yarn is rarer than Gems. It's the primary currency for bribing Cat Guards in the upper floor of Gift Shop for new weapons, but it can also be traded with other players. Each level has a single Yarn that is usually hidden or hard to reach. Unlike Gems, Yarn can't be hidden inside of a fake block.

https://steamhost.cn/steamcommunity_com/id/Freekill/inventory/#238460_2_41880040

Each weapon costs 5 Yarn meaning that you need a total of 60 Yarn for all 12 weapons. After you buy all weapons you will start to horde unneeded Yarn.

Used in Community Theater Levels, the Strawberry take the place of Gems to prevent Gem farming. Three Strawberries are required to unlock the exit in Adventure Levels. Just like Gems, Strawberries can be hidden inside of blocks.

Cannot be used to unlock Prisoners and it will not store in user's Steam Inventory.

Used in Community Theater Levels, the Pumpkin Pie takes the place of the Yarn to prevent Yarn farming. As it takes place instead of the Yarn you can expect it in hard to reach places, it cannot be hidden inside of a block.

Cannot be used to purchase Weapons and it will not store in user's Steam inventory.

The Golden Hat is spawns during any levels at both random location and time. Only the player that finishes the level with the Golden Hat will get an additional 10 Gems, so, naturally, this is a friendship destroyer.

If the Player dies with the Golden Hat he will need to retrieve it again but, be careful, if the Golden Hat falls in the water it will disappear!

The Golden Hat closely resembles Hatty Hattington's Hat, but colored gold.